[PATCH AUTOSEL for 4.4 16/20] IB/mlx4: Increase maximal message size under UD QP

[alexander.levin@verizon.com]

From: Mark Bloch <markb@mellanox.com>

[ Upstream commit 5f22a1d87c5315a98981ecf93cd8de226cffe6ca ]

Maximal message should be used as a limit to the max message payload allowed,
without the headers. The ConnectX-3 check is done against this value includes
the headers. When the payload is 4K this will cause the NIC to drop packets.

Increase maximal message to 8K as workaround, this shouldn't change current
behaviour because we continue to set the MTU to 4k.

To reproduce;
set MTU to 4296 on the corresponding interface, for example:
ifconfig eth0 mtu 4296 (both server and client)

On server:
ib_send_bw -c UD -d mlx4_0 -s 4096 -n 1000000 -i1 -m 4096

On client:
ib_send_bw -d mlx4_0 -c UD <server_ip> -s 4096 -n 1000000 -i 1 -m 4096

Fixes: 6e0d733d9215 ("IB/mlx4: Allow 4K messages for UD QPs")
Signed-off-by: Mark Bloch <markb@mellanox.com>
Reviewed-by: Majd Dibbiny <majd@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
---
 drivers/infiniband/hw/mlx4/qp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/infiniband/hw/mlx4/qp.c b/drivers/infiniband/hw/mlx4/qp.c
index 1c8b7c22c822..348828271cb0 100644
--- a/drivers/infiniband/hw/mlx4/qp.c
+++ b/drivers/infiniband/hw/mlx4/qp.c
@@ -1564,7 +1564,7 @@ static int __mlx4_ib_modify_qp(struct ib_qp *ibqp,
 			context->mtu_msgmax = (IB_MTU_4096 << 5) |
 					      ilog2(dev->dev->caps.max_gso_sz);
 		else
-			context->mtu_msgmax = (IB_MTU_4096 << 5) | 12;
+			context->mtu_msgmax = (IB_MTU_4096 << 5) | 13;
 	} else if (attr_mask & IB_QP_PATH_MTU) {
 		if (attr->path_mtu < IB_MTU_256 || attr->path_mtu > IB_MTU_4096) {
 			pr_err("path MTU (%u) is invalid\n",
-- 
2.11.0